Cobaltaustinite is a rare arsenic-bearing mineral known for its vibrant green color caused by cobalt substitution. It typically occurs as small, crusty, or botryoidal growths in oxidized polymetallic ore deposits. Collectors prize it primarily for its distinct color and association with other rare secondary arsenate minerals.
Is this cobaltaustinite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch cobaltaustinite with a known reference. Cobaltaustinite sits at Mohs ~4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale green.
- 3Read the lusterHold the specimen under a strong light. Luster: earthy.
- 4Match the color rangeCompare against the expected color range: green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crusts, botryoidal aggregates, acicular crystals.
Often confused with
Cobaltaustinite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cobaltaustinite leaves pale green, Austinite leaves white; luster reads earthy on Cobaltaustinite and subadamantine to silky in aggregates on Austinite.
How to tell apart: Streak differs, so Cobaltaustinite leaves pale green, Conichalcite leaves green; luster reads earthy on Cobaltaustinite and vitreous to somewhat greasy on Conichalcite.
Often found alongside cobaltaustinite
Minerals reported to co-occur with cobaltaustinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCo(AsO₄)(OH)
- Mohs hardness
- ~4.5
- Density
- 4.24 g/cm³
- Colors
- Streak
- Pale green
- Luster
- Earthy
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Crusts, botryoidal aggregates, acicular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of a copper deposit, an alteration product of arsenides
Where rockhounds find cobaltaustinite
Classic worldwide localities
- Dome Rock copper mine, about 40 km northwest of Mingary, South Australia
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of a copper deposit, an alteration product of arsenides. If you start seeing erythrite, roselite-beta, arthurite in float, you are in the right ground. Typical habit: crusts, botryoidal aggregates, acicular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cobaltaustinite?+
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What rocks look like cobaltaustinite?+
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Find cobaltaustinite on the map
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